Using encoders

In the previous examples, we exchanged messages only of type string. Sometimes, we may need to transfer more complex objects to the client, a Movie instance, for example, holding information such as the movie title, actors, and so on. From a RESTful background, the most popular solution is to convert the object to a JSON string. Rather than doing this manually before using the sendText(String) method, we can define a custom encode that automatically converts the object to the desired format.

Let's look at the following example:

@ServerEndpoint(value = "/movie/{movieId}",  
        encoders = {MovieEncoder.class}) 
public class MoviesEndpoint{ 
     
     
    public void onOpen(Session session, EndpointConfig endpointConfig) { 
        Movie movie = new Movie(); 
        try { 
            // fill with some data 
            session.getBasicRemote().sendObject(movie); 
        } catch (IOException | EncodeException ex) { 
            ex.printStackTrace(); 
        } 
    } ...